The ultimate objective of this program project application is to understand the pathophysiology of acute and chronic graft-vs.-host disease (GVHD) in humans. To achieve this objective, skin samples and blood specimens from patients will be collected, catalogued, and distributed to the relevant projects for analysis of lymphocytes, chemokines, cytokines, and minor histocompatibility antigen. Individual patient data will he collected for the clinical studies and to provide laboratory observations with clinical correlates. The focus of all projects is to develop targeted strategies that can control GVHD while maintaining graft-vs.-leukemia effects. Integrated data management and specimen tracking are critical for all three projects and extend beyond patient care and clinical laboratory functions. Without the clinical research support provided in the Core it would be impossible to coordinate the proper collection of multiple research samples, assure appropriate tracking of specimens, collect detailed patient-level data, and ensure the highest quality data are available to achieve laboratory and clinical objectives. This core will interact extensively with Dr. Haesook Kim from the Biostatistics Core C who will provide assistance in study design and analysis for the Projects. The purpose of the Data Management and Specimen Tracking Core D is to provide the following services that will be utilized by all three Projects: 1. To help clinical and laboratory investigators identify the necessary patient-level information for their projects, and to design forms, procedures and databases to capture these data. 2. To provide clinical data management for abstraction of individual patient information. 3. To provide a central mechanism for specimen collection, identification and tracking between the three projects. 4. To provide data management support and quality control for clinical data.